Gas burners have been used in fireplaces and similar heating devices both as a primary heat source, often with ceramic logs, and as a wood starter. Gas burners burn cleaner than wood and provide a simple, clean way to start wood fires.
While gas burners have advantages, they can impose the serious threat of gas leakage from a non-burning gas source. When gas is allowed to escape under the atmospheric pressure conditions, it can form a highly explosive and generally toxic mixture with the ambient air.
Prior art gas burners for wood fire starting also require manual shutoff. Thus, if a casual user forgets to turn off the gas supply, the gas will remain burning wasting fuel.
Various safety systems have been designed to protect against gas leakage when the burner fails to light or when there exists a temporary interruption in the gas supply. Such systems include the traditional draft hood, measuring pilot burner temperature as in U.S. Pat. No. 3,111,161 and measuring the temperature in a blast tube of a power gas burner as in U.S. Pat. No. 4,655,705. However, these systems do not provide automatic controls for a solid fuel starter. Furthermore, the draft hood is inefficient as a safety device because it draws unnecessary air out of the home, and when combined with spillage detection, it becomes expensive to operate. Powered burners are also costly and have not gained wide acceptance in dual fuel appliances.
Having the ability to burn either gas or solid fuel in the same combustion chamber gives the user the option of what fuel to use and makes starting a wood fire easier and cleaner. While gas fire starters for fireplaces have been used for many years, they generally do not have optimum safety controls and are generally not approved for use with liquid propane gas which is heavier than air.